Effects of met-enkephalin on electrical coupling between identified neurons in the pulmonate snails, Helix and...

1. The effects of met-enkephalin on electrical coupling between molluscan neurons have been investigated using the isolated brains of Helix pomatia and Lymnaea stagnalis. 2. In the presence of both serotonin and met-enkephalin, non-rectifying electrical coupling is strongly facilitated between identified respiratory neurons in Helix, whilst coupling between putative, serotonin-containing, ciliomotoneurons in Lymnaea is facilitated by met-enkephalin alone. 3. Facilitation of coupling by met-enkephalin is weaker in the strongly coupled neurons, VD1/RPaD2 of Lymnaea. 4. These data suggest that met-enkephalin can modulate different groups of electrically coupled cells and may be involved in coordination of motor patterns.